html {

    font-size : 16px;

}

@media only screen and (max-width: 1080px),only screen and (max-width:1080px) {
     html,body {
    font-size: 20px
    }
  }

@media only screen and (max-width: 960px),only screen and (max-width:960px) {
    html,body {
        font-size:20px
    }
}

@media only screen and (max-width: 720px),only screen and (max-width:720px) {
    html,body {
    font-size: 16px
    }
  }

button{
    font-size: 16px;
}